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EC number: 293-917-2
CAS number: 91648-55-4
The category consists of alkyl sulfates with a predominantly linear
alkyl chain length of C8-C20. Most chemicals of this category are not
defined substances, but mixtures of homologues with different alkyl
chain lengths (UVCBs). The most important common structural feature of
the category members is the presence of a predominantly linear aliphatic
hydrocarbon chain with a polar sulfate group, neutralized with a counter
ion (i.e., Na+, K+, NH4+, ethanolamine or monoisopropanolamine cation).
The hydrophobic hydrocarbon chain (with a length between C8 and C20) and
the polar sulfate group confer surfactant properties and enable the
commercial use of these substances as anionic surfactants. Common
physical and biological pathways result in structurally similar
breakdown products, and are, together with the surfactant properties,
responsible for similar environmental behavior and essentially identical
hazard profiles with regard to human health. The counter ion will not
influence chemical reactivity and classification for the purpose of this
assessment is not expected to be affected by the difference in counter
ion (ref. OECD SIDS 2007, HERA Report 2002, Koennecker et al. 2011).
In aqueous environments the salts will dissociate, so that the counter
ions will not fundamentally alter pathways of tissue disposition,
metabolism, excretion, or target organs of toxicity. Accordingly no
major differences were found in most of the endpoints between the
compounds with different counter ions (ref. OECD SIDS 2007, HERA Report
2002, Koennecker et al. 2011). Moreover, several of the counter-ions
have also been assessed in the OECD HPV Program and/or according to
REACH Regulation (EC) No 1907/2006: ethanolamine (CAS 141-43-5)
triethanolamine (CAS 102-71-6), monoisopropanolamine (CAS 78-96-6), the
ammonia category (CAS 7664-41-7; 1336-21-6; 7783-18-8; 12593-60-1) and
ammonium salts, like ammonium sulfate (CAS 7783-20-2), chloride (CAS
12125-02-9) and bicarbonate (CAS 1066-33-7).
In accordance with Article 13 (1) of Regulation (EC) No 1907/2006,
"information on intrinsic properties of substances may be generated by
means other than tests, provided that the conditions set out in Annex XI
are met. In particular for environmental fate and eco-toxicity,
information shall be generated whenever possible including the use of
information from structurally related substances. In this particular
case the similarity of the alkyl sulfates category members is justified,
in accordance with the specifications listed in Regulation (EC) No.
1907/2006 Annex XI, 1.5 Grouping of substances and read-across, is based
on the scope of overlapping of composition, similar molecular structure,
physico-chemical properties, toxicological, ecotoxicological profiles
and supported by various QSAR methods.
Physico-chemical properties relevant for environmental fate of alkyl
Physico-chemical characteristics of the substances in the category are
similar, or follow regular patterns. The most important parameter
influencing PC-properties is the varying length of the alkyl chain.
- Vapor pressure - as ionic substances, category members are
characterized by low vapor pressures.
- Partition coefficient - as surfactants concentrate at
hydrophilic/hydrophobic boundaries and do not equilibrate between
phases, Pow is not a good descriptor of surfactant hydrophobicity and
only of a limited predictive value for the partitioning of these
compounds in the environment. Nevertheless, experimental Pow values have
been obtained, usually as quotients of solubilities in octanol and in
water. Partition coefficients are normally low and they increase with
the alkyl chain range.
- Water solubility - the solubility in water of the category members is
in the range of 1-1000 g/L. Particular values decrease with the alkyl
Environmental fate and pathways of alkyl sulfates:
- The substances are readily biodegradable. Abiotic degradation (e.g.
hydrolysis) is not a relevant for environmental pathway due to the
chemical structure of the substances.
- Due to the low to moderate log Koc-value, it can be predicted that the
sorption to sludge, sediments and soils will be relatively low. Alkyl
sulfates are unlikely to persist in the aquatic environment.
Aquatic toxicity of alkyl sulfates:
For the alkyl sulfate category many tests are available on the acute and
long-term toxicity to fish, invertebrates and algae, conducted with
single-chain homologues as well as with technical mixtures. The results
demonstrate that invertebrates are the most sensitive trophic level,
followed by fish and algae. The most important influencing parameter for
fish and invertebrate toxicity within the alkyl sulfates category is the
chain length of the alkyl group.
Short-term toxicity to fish is well studied for the category of alkyl
sulfates and includes tests with substances of chain lengths ranging
from C8 to C18 covering a variety of both freshwater and marine species.
Alkyl sulfates of chain lengths from C8 to C12 seem to have low to
moderate toxicity. Homologues from C13 to C15 are more toxic than C8 to
C12. Toxicity of the chain lengths from C16 and higher is inconsistent,
but in general these substances are less toxic than C13 to C15. This
most probably can be explained by variable bioavailability as a
consequence of reduced water solubility.
The influence of the chain length of alkyl sulfates on the acute
toxicity fish is comparable to invertebrate toxicity (OECD SIDS, 2007).
Also in this case a clear correlation can be shown since the available
database includes the studies for the alkyl sulfates ranging from C8 to
C18. Short-term toxicity to aquatic invertebrates increases with
increasing length of the hydrocarbon chain up to C16 and then decreases.
Available long-term tests on fish with alkyl sulfates show that the
toxicity depends again on the substance chain length. The same pattern
as in the acute tests was observed - homologues C12 and C18 are less
toxic than the chain lengths C14-C15 (OECD SIDS, 2007).
Available information on the long-term toxic effects of alkyl sulfates
to Ceriodaphnia dubia includes the substances with a carbon chain length
from C10 to C18. A clear response curve was observed - toxicity increase
with chain length from C12 to C14 and then decreased up to C18. Since
C18 AS is insoluble in calcium-containing water (i.e., Ceriodaphnia test
waters), the effects are due to physical interactions, not the classic
uptake into the organism and then elicit toxicity. Chronic toxicity
testing with Daphnia magna using the technical product C14-15 proved
that these are the most toxic chain lengths for aquatic invertebrates
(OECD SIDS, 2007).
Several reliable experimental studies with algae are available for alkyl
sulfates. It seems that algae are less sensitive to alkyl sulfate
exposure than fish and invertebrates. The results do not allow the clear
prediction of a chain length dependency of algal toxicity because most
of the studies were conducted with technical products. Nevertheless, it
seems that the most toxic chain lengths are C14 and C15 (OECD SIDS,
Activated sludge respiration inhibition and Pseudomonas putida tests are
available for the alkyl sulfates of chain lengths from C12 to C18. In
Pseudomonas putida, a tendency for increasing toxic effects with
increasing carbon chain length could be observed (OECD SIDS, 2007).
Acute toxicity key values for C16-20AS Na (CAS 91648-55-4):
- For fish: 96h LC50 (Danio rerio, mortality) = 5.2 mg/L (nominal
concentration, ISO 7346-1, read across from CAS 68955-20-4)
- For invertebrates: 48h EC50 (Daphnia magna, mobility) = 37.91 mg/L
(WAF, OECD 202)
- For algae: 72h EC50 (Desmodesmus subspicatus, growth rate) = 34 mg/L
(nominal concentration, DIN 38412 (9), read-across from CAS 68955-20-4)
Chronic toxicity key values for C16-20AS Na (CAS 91648-55-4):
- For fish: 14d NOEC (Pimephales promelas, mortality and growth) = 1.65
mg/L (nominal concentration, OECD 204, read-across from CAS 68955-20-4)
- For invertebrates: 7d NOEC (Ceriodaphnia dubia, reproduction) = 0.204
mg/L (measured concentration, EPA-600/489/001, read-across from CAS
- For algae: 72h EC10 (Desmodesmus subspicatus, biomass) = 19 mg/L
(nominal concentration, DIN 38412 (9), read-across from CAS 68955-20-4)
Toxicity to microorganisms of C16-20AS Na (CAS 91648-55-4):
- For microorganisms 18h NOEC (Pseudomonas putida, growth inhibition) =
550 mg/L (nominal concentration, read-across from CAS 68955-20-4)
Information on Registered Substances comes from registration dossiers which have been assigned a registration number. The assignment of a registration number does however not guarantee that the information in the dossier is correct or that the dossier is compliant with Regulation (EC) No 1907/2006 (the REACH Regulation). This information has not been reviewed or verified by the Agency or any other authority. The content is subject to change without prior notice.Reproduction or further distribution of this information may be subject to copyright protection. Use of the information without obtaining the permission from the owner(s) of the respective information might violate the rights of the owner.
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